[Qemu-devel] Misbehavior of qemu ppc tcg/translation?

[Baojun Wang]

hi, list:

  I hope the following example is self-explained, in the assembler
code, we can use instruction like (instruction-as-data?):

                100000b4:       10 00 12 34     .long 0x10001234

  but the ppc translator set the exception flag and raise a PROGRAM
exception later, however on real machine, if the above instruction is
never ran, then everything should be OK. Thus the ppc translator raise
the exception too early? (I think it should only raise the PROGRAM
exception until tcg really trying to exec the instruction, but not on
translation time)

  Thanks,
Wang Baojun

$ qemu-ppc -L emu-ppc ./hello
hello, world!
invalid/unsupported opcode: 04 - 1a - 08 (10001234) 100000b4 0
Invalid instruction
NIP 100000b8   LR 100000b4 CTR 00000000 XER 00000000
MSR 00006040 HID0 00000000  HF 00006000 idx 0
TB 00000000 00000000
GPR00 0000000000000004 000000004007f588 0000000000000000 000000000000000f
GPR04 00000000100100c4 000000000000000f 0000000000000000 0000000000000000
GPR08 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR12 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR16 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR24 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR28 0000000000000000 0000000000000000 0000000000000000 0000000000000000
CR 00000000  [ -  -  -  -  -  -  -  -  ]             RES ffffffff
FPR00 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR04 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR08 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR12 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR16 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR20 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR24 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR28 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPSCR 00000000
Segmentation fault


on a real machine:
$ ./hello
hello, world!
$ powerpc-unknown-linux-gnu-objdump -d hello

hello:     file format elf32-powerpc

Disassembly of section .text:

10000094 <_raw_write>:
10000094:       44 00 00 02     sc
10000098:       4e 80 00 20     blr

1000009c <_start>:
1000009c:       38 00 00 04     li      r0,4
100000a0:       38 60 00 01     li      r3,1
100000a4:       3c 80 10 01     lis     r4,4097
100000a8:       38 84 00 c4     addi    r4,r4,196
100000ac:       38 a0 00 0f     li      r5,15
100000b0:       4b ff ff e5     bl      10000094 <_raw_write>
100000b4:       10 00 12 34     .long 0x10001234
100000b8:       38 00 00 01     li      r0,1
100000bc:       38 60 00 00     li      r3,0
100000c0:       44 00 00 02     sc